SRU Training Module.pdf

7/21/2019 SRU Training Module.pdf

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TRAINING MODULE DOC NO: 8474L-022-A5016-0000-001-012

SULPHUR RECOVERY UNIT (SRU) REV: 0 DATE: 21/03/08

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TRAINING MODULE

SULPHUR RECOVERY UNIT (SRU)

UNIT: 22

0 21/03/08 Benoit Rabaud Paul Walsh JB Guillemin

A 29/11/07 Benoit Rabaud Paul Walsh JB Guillemin

REV DATE PREPARED BY CHECKED BY APPROVED BY

TRAINING DURATION VENUE

ATTENDANCE

ATTENDEES REQUIREMENTS

MODULE OBJECTIVES

INSTRUCTORS NAME/POSITION

SUMMARY/AGENDA


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IMPORTANT

THIS TRAINING MODULE HAS BEEN PREPARED BY ARAMIS FOR THE DUNG QUATREFINERY.

THIS MODULE MUST BE RECOGNIZED AS A TOOL AND GUIDE ONLY. IT WOULD BEIMPOSSIBLE TO ANTICIPATE AND PRESENT ALL POTENTIAL VARIABLES AND

PROCESS CONDITIONS THAT OPERATIONAL PERSONNEL MIGHT BE EXPOSED TO.

IT IS IMPERATIVE THAT THE READER ALWAYS AS CERTAIN THAT REFERENCEMATERIALS UTILIZED, WHILE PERFORMING OPERATIONAL DUTIES, CONFORM AT A

MINIMUM TO THE LATEST ISSUE OF STANDARD OPERATING PROCEDURES, SAFETYCODES, ENGINEERING STANDARDS, AND GOVERNMENT REGULATIONS.

SOME DESIGN FIGURES MIGHT NOT BE IN LINE DURING THE START-UP OF THEREFINERY.


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TABLE OF CONTENT

SECTION 1 : GENERAL description ......................................................................................... 10

1.1. Purpose of the Unit ............................................................................................... 131.2. Basis of Design .................................................................................................... 15

1.2.1. Duty of Plant .............................................................................................. 15

1.2.2. Feed Characteristics ................................................................................. 15

1.2.2.1. Feed Composition & Capacity for production of degassed liquidsulphur 15

1.2.2.2. Feed Composition and Capacity to Incinerator ............................ 16

1.2.2.3. Designed Feed Composition and Capacity for Production ofDegassed Liquid Sulphur........................................................................... 17

1.2.3. Product Specifications ............................................................................... 19

1.2.3.1. Degassed Liquid Sulphur Specifications ...................................... 19

1.2.3.2. Emissions from Incinerator ........................................................... 19

1.2.4. Utility/Power/Chemicals/Catalyst consumption.......................................... 19

1.2.4.1. Utility Consumption ...................................................................... 19

1.2.4.2. Catalysts & Chemicals ................................................................. 22

1.3. Glossary of terms and Acronyms ......................................................................... 24

1.3.1. Acronyms .................................................................................................. 24

1.3.2. Glossary .................................................................................................... 27

SECTION 2 : Process Flow Description .................................................................................... 29

2.1. Claus Section ....................................................................................................... 31

2.1.1. ARU Off Gas from Unit 19 & H2S Rich Off Gas from Unit 18 .................... 31

2.1.2. Combustion air feeding to Claus section ................................................... 31

2.1.3. Thermal Reactor and Burner ..................................................................... 32

2.1.4. Claus Waste Heat Boiler and 1stSulphur Condenser ................................ 33

2.1.5. 1stProcess Gas Reheater & 1stCatalytic Reactor ..................................... 33

2.1.6. 2nd

Condenser, 2nd

Process Gas Reheater & 2nd

Catalytic Reactor .......... 342.1.7. 3rdCondenser, 3rdProcess Gas Reheater & 3rdCatalytic Reactor ............ 34

2.1.8. Final Sulphur Condenser and Tail Gas Coalescer .................................... 36

2.2. Liquid Sulphur Storage Pit .................................................................................... 36

2.3. Sulphur Degassing Section .................................................................................. 37

2.4. Incinerator Section ............................................................................................... 39

2.5. DCS Printouts SRU Process Overview ............................................................. 39

SECTION 3 : Process control .................................................................................................... 44


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3.1. Control narrative & operating parameters ............................................................ 44

3.1.1. ARU Off Gas KO Drum A-2201-D-01 Pressure Control ............................ 44

3.1.2. H2S Rich SWS Off Gas KO Drum A-2201-D-02 Pressure Control ............ 46

3.1.3. A-2201-D-01/02/03 Level Control .............................................................. 503.1.4. Thermal Reactor Combustion Air Control .................................................. 52

3.1.4.1. Main Combustion Air Flowrate to Thermal Reactor...................... 52

3.1.5. Trim Air Flow to Thermal Reactor Control by Tail Gas Analysis ................ 55

3.1.6. Quench Steam Flowrate Control ............................................................... 56

3.1.7. Combustion Air to Incinerator Flowrate Control (A-2201-H-01) ................. 58

3.1.7.1. Incinerator Residence Zone Temperature Control (A-2201-H-01) 60

3.1.8. Inter-Unit Controls & Interfaces ................................................................. 62

3.1.9. Operating Parameters ............................................................................... 62

3.2. Instrument List ...................................................................................................... 62

3.3. Main Equipment ................................................................................................... 63

3.3.1. Thermal Reactor ........................................................................................ 63

3.3.2. Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 ........................ 66

3.3.3. Catalytic Reactors A-2201-R-02/03/04 ...................................................... 73

3.3.4. Liquid Sulphur Storage Pit A-2201-TK-01 & Degassing Tank A-2201-TK-02 75

3.3.5. Incinerator A-2201-H-01 ............................................................................ 78

3.3.6. Blowers ..................................................................................................... 81

SECTION 4 : Safeguarding devices .......................................................................................... 85

4.1. Alarms and Trips .................................................................................................. 85

4.2. Safeguarding Description ..................................................................................... 85

4.2.1. Interlock UX-501 General ESD ............................................................... 85

4.2.2. Interlock UX-502 Incinerator ESD .......................................................... 87

4.2.3. Interlock UX-503 Thermal Reactor ESD ................................................. 92

4.2.4. Interlock UX-504 A-2201-B-01 A/B Protection ....................................... 97

4.2.5. Interlock UX-505 A-2201-P-01 A/B Protection ....................................... 97



4.2.8. Interlock UX-508 Sulphur Degassing ESD ............................................. 99

4.2.9. Interlock UX-509 A-2201-P-05 A/B Protection ..................................... 100

4.3. Safeguarding Equipment .................................................................................... 102

4.3.1. Pressure Safety Devices ......................................................................... 102

SECTION 5 : Fire & Gas Systems ........................................................................................... 105


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5.1. Fire & Gas detection ........................................................................................... 105

5.2. Fire Protection .................................................................................................... 108

5.2.1. Precautionary measures to avoid fuel gas explosions in Claus area ....... 111

5.2.2. Precautionary measures to avoid sulphur burning .................................. 1125.2.3. Extinguishing Sulphur Pit fires ................................................................. 112

5.2.4. Sulphur Fires ........................................................................................... 112

SECTION 6 : Quality control .................................................................................................... 116

6.1. Sampling Analysis .............................................................................................. 116

6.1.1. Sampling Connections ............................................................................ 117

6.1.2. Sampling Frequency ............................................................................... 117

6.1.3. Safe handling of samples ........................................................................ 118

6.1.3.1. Handling of gas samples containing H2S ................................... 1186.1.3.2. Handling of liquid sulphur ........................................................... 118

6.2. On-line analysers ............................................................................................... 118

SECTION 7 : Causes and effect .............................................................................................. 121

7.1. Cause & Effect Matrix: ........................................................................................ 121

7.1.1. Example from Cause and Effect Chart .................................................... 121

7.1.1.1. UX-502: Incinerator ESD ............................................................ 121

SECTION 8 : Operating practices ............................................................................................ 126

8.1. Normal Operation ............................................................................................... 1268.1.1. Operating conditions ............................................................................... 126

8.1.2. Combustion air / acid gas ratio and Thermal Reactor temperature ......... 135

8.1.3. Claus Reactors Temperatures in normal operating conditions ................ 136

8.1.4. Claus Reactors Temperatures during sulphur sweeping operations ....... 136

8.1.5. Incinerator temperature ........................................................................... 137

8.1.6. Process Variable Effect on Product Quality ............................................. 137

8.1.7. Process Variable Effect on Sulfur Yield ................................................... 137

8.1.8. Sulphur Degassing Section ..................................................................... 138

8.2. Start-up Procedure ............................................................................................. 138

8.2.1. Preparation for Initial Start-Up ................................................................. 139

8.2.2. Initial Start-up .......................................................................................... 140

8.2.3. Plant Re-start-up following a shutdown ................................................... 142

8.2.3.1. Quick restart of warm plant ........................................................ 142

8.2.3.2. Restart of cold plant ................................................................... 142

8.3. Shutdown Procedures ........................................................................................ 143


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8.3.1. Planned Shutdown .................................................................................. 143

8.4. Emergency Shutdown ........................................................................................ 145

8.4.1. Emergency Shut-down System Activation ............................................... 145

8.4.2. Power Failure .......................................................................................... 1458.4.3. Lack of Feedstock ................................................................................... 145

8.4.4. Failure of Liquid Sulphur Export Line ...................................................... 146

8.4.5. Instrument Air Failure .............................................................................. 146

8.4.6. Steam Failure .......................................................................................... 146

8.4.7. Boiler Feed Water Failure ....................................................................... 146

8.4.8. Fuel Gas Failure ...................................................................................... 147

8.4.9. Combustion Air Blowers (A-2201-B-01A/B) Failure ................................. 147

8.4.10. Incinerator Combustion Air Blowers (A-2201-B-02AIB) Failure ............. 147

8.4.11. Dilution Air Blowers (B-2203A/B) Failure ............................................... 147

8.4.12. Off Gas K.O. Drum Pumps (A-2201-P-01A/B, 02A/B, 03A/B) Failure ... 148

8.4.13. Sulphur Circulation and Sulphur Pumps (A-2201-P-04A/B, 05A/B) Failure 148

SECTION 9 : HSE ................................................................................................................... 150

9.1. Hazardous Areas ................................................................................................ 150

9.1.1. Prevention of H2S and SO2 leaks ........................................................... 152

9.2. Safety Equipment ............................................................................................... 152

9.3. Specific PPE....................................................................................................... 152

9.3.1. H2S ......................................................................................................... 152

9.3.2. Sulphur Dioxide ....................................................................................... 153

9.3.3. Sulphur .................................................................................................... 153

9.4. Chemical Hazards .............................................................................................. 154

9.4.1. Hydrogen Sulfide Toxicity ........................................................................ 154

9.4.1.1. Acute Hydrogen Sulfide Poisoning ............................................. 154

9.4.1.2. Subacute Hydrogen sulfide Poisoning ....................................... 155

9.4.2. Sulphur Dioxide Toxicity .......................................................................... 156

9.4.3. Sulphur .................................................................................................... 157

9.4.4. Process gas and tail gas ......................................................................... 157

SECTION 10 : Reference documents index ............................................................................ 159

10.1. Operating Manual/ Licensor Documentation ...................................................... 159

10.2. Arrangement Drawings, Layouts and Plot Plans ................................................ 159

10.3. Process Flow Diagrams ..................................................................................... 159

10.4. Piping and Instrumentation Diagrams ................................................................ 159


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10.5. Equipment list ..................................................................................................... 160

10.6. Main Equipment Data Sheet............................................................................... 160

10.7. Instrument List .................................................................................................... 160

10.8. Cause & Effect Matrix ......................................................................................... 16010.9. Safety Logic diagram .......................................................................................... 160

10.10. Fire & Gas Cause & Effect Chart ............................................................. 160

10.11. Fire & Gas Detectors Layout ................................................................... 160

10.12. Fire Protection Layout.............................................................................. 161

10.13. Hazardous Area Classification ................................................................. 161

10.14. MSDS ...................................................................................................... 161

10.15. Vendors Documentation .......................................................................... 161


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TRAINING MODULE


UNIT: 22

Course Content:

Section 1 - General Description

XSection 2 - Process Flow DescriptionSection 3 - Process Control

Section 4 - Safeguarding Devices

Section 5 - Fire & Gas Systems

Section 6 - Quality Control

Section 7 - Cause & Effects

Section 8 - Operating Procedures

Section 9 - HSE

Section 10 - Reference Document Index


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SECTION 1 : GENERAL DESCRIPTION

The Sulphur recovery Unit (SRU) has been designed for the Bach Ho crude operation to convert

all suphur compounds present in the acid gas feed from the ARU and the SWS into liquidelemental sulphur. First a part of H2S is burned and converted into SO2 while the remainingreacts with SO2to give elemental sulphur before being condensed. The produced liquid sulphuris then degassed and cleared from dissolved H2S. Treated gas is finally incinerated to convertthe remaining pollutants into SO2.

The SRU is located at the south west of the area 4, next to the LCO HDT, ARU and SWS units.


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Figure 1: 2D Refinery Plot Plan


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Figure 2: 3D Refinery Plot Plan


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1.1. Purpose of the Unit

The scope of the Sulphur Recovery Unit (SRU) is to convert all sulphur compoundspresent in the acid gas feeds into liquid elemental sulphur,

This unit consists of the following sections:

Section Purpose

Sulphur Recovery (Claus)Section

Section based on the Claus Process where the major scope is toconvert H2S into elemental liquid sulphur.

Section composed of a thermal stage (Thermal Reactor) followedby 3 catalytic steps:

The purpose of the thermal reactor is to burn approx. 1/3 of the H2Scontained in the total acid gases feed with air to convert it into SO 2.(Reaction H2S + 3/2 O2= SO2+ H2O)

The purpose of the catalytic converters is to make the remaining 2/3of the H2S react with the produced SO2 to give elemental sulphur(Reaction: 2 H2S + SO2= 3/x SX+ H2O)

In the Claus section, produced sulphur is also condensed.

The overall recovery of the Claus section is approx 96.5% at designconditions.

Liquid Sulphur Storageand Degassing Section

The scope of the Degassing Section is to ensure the liquid sulphurdegassing and to remove the dissolved H2S from the producedsulphur, in order to avoid H2S local pollution (H2S desorbed fromliquid sulphur) and toxic/explosion hazards during sulphur handling.

With this section, H2S content in the liquid sulphur is decreased toless than 20 wt. ppm (much below the explosivity of H2S with air)

Incinerator Section The purpose of the incinerator section is to convert residual H2Scontained in the treated gas leaving the Claus section and thedegassing section into SO2and to finally discharge the flue gas tothe atmosphere through the stack.

NH3rich SWS off gas and CNU off gas are also incinerated here.

Sulphur Apron The sulphur apron is where is collected the solid sulphur from thedegassing pit.


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Figure 3: Unit 22 - 3D Drawing

SRU


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1.2. Basis of Design

1.2.1. Duty of Plant

The SRU ahs been designed to recover sulphur from the following acid gas

streams:

ARU off gas (from unit 019)

H2S rich off gas (from unit 018)

The Incinerator Unit has been designed to directly treat the following acid gases:

NH3rich off gas from SWS (unit 018)

CNU off gas (unit 020)

The Sulphur Degassing Section has been designed to treat the total sulphurproduced by the Claus Unit at design capacity.

The SRU is designed for a production capacity of 5 ton/day of produced degassedliquid sulphur with a Sulphur Recovery Efficiency (SRE) of 95% minimum of thesulphur entering the SRU.

The SRU can operate in steady conditions in the range of 50% to 100% of thedesign conditions.

1.2.2. Feed CharacteristicsThe SRU has been designed to treat 2 feed cases of the BACH HO CRUDE:

Max Distillate Case

Max Gasoline Case

1.2.2.1. Feed Composition & Capacity for production of degassed liquid sulphur

1.2.2.1.1. ARU Off Gas FeedStock Specifications

Max. Distillate Case Max. Gasoline CaseComposition kg/hr kg-mol/hr Mol% kg/hr kg-mol/hr Mol%

H2S 102.6 3.01 18.97 119.6 3.51 20.66

NH3 0.0 0.00 0.00 0.0 0.00 0.00

H2O 16.5 0.92 5.77 19.0 1.05 6.21

Cyanide 0.0 0.00 0.00 0.0 0.00 0.00

CO2 511.4 11.62 73.24 531.4 12.08 71.11

N2 1.0 0.04 0.23 1.0 0.04 0.21


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Max. Distillate Case Max. Gasoline Case

Composition kg/hr kg-mol/hr Mol% kg/hr kg-mol/hr Mol%

CO 0.1 0.004 0.02 0.1 0.00 0.02

H2 0.3 0.15 0.94 0.3 0.15 0.87

C1 1.4 0.09 0.55 1.6 0.10 0.59

C2 1.1 0.04 0.23 1.1 0.04 0.22

C3 0.4 0.01 0.06 0.8 0.02 0.11

Total 634.8 15.87 100.00 674.9 16.98 100.00

1.2.2.1.2. SWS H2S Rich Off Gas Feedstock Specifications



H2S 82.0 2.41 88.94 50.3 1.48 88.09

NH3 0.0 0.00 0.00 0.0 0.00 0.00

H2O 4.8 0.27 9.96 3.1 0.17 10.12

Cyanide 0.7 0.03 1.10 0.7 0.03 1.79

CO2 0.0 0.00 0.00 0.0 0.00 0.00

N2 0.0 0.00 0.00 0.0 0.00 0.00

CO 0.0 0.00 0.00 0.0 0.00 0.00

H2 0.0 0.00 0.00 0.0 0.00 0.00

C1 0.0 0.00 0.00 0.0 0.00 0.00

C2 0.0 0.00 0.00 0.0 0.00 0.00

C3 0.0 0.00 0.00 0.0 0.00 0.00

Total 87.5 2.71 100.00 54.1 1.68 100.00

1.2.2.2. Feed Composition and Capacity to Incinerator

1.2.2.2.1. SWS NH3Rich Off Gas FeedStock Specifications



H2S 14.7 0.43 3.24 8.9 0.26 2.76

NH3 157.6 9.27 69.75 112.3 6.61 70.25


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H2O 64.7 3.59 27.01 45.7 2.54 26.99

Cyanide 0.0 0.00 0.00 0.0 0.00 0.00

CO2 0.0 0.00 0.00 0.0 0.00 0.00

N2 0.0 0.00 0.00 0.0 0.00 0.00

CO 0.0 0.00 0.00 0.0 0.00 0.00

H2 0.0 0.00 0.00 0.0 0.00 0.00

C1 0.0 0.00 0.00 0.0 0.00 0.00

C2 0.0 0.00 0.00 0.0 0.00 0.00

C3 0.0 0.00 0.00 0.0 0.00 0.00

Total 237.0 13.29 100.00 166.9 9.41 100.00

1.2.2.2.2. CNU Off Gas Feedstock Specifications

Naphtenic /Sulfidic Sour(Mixed Crude)

Naphtenic /Sulfidic Sweet

(Bach Ho Crude)

Phenolic Sour(Mixed Crude)

Phenolic Sweet(Bach Ho Crude)

Std Vol. Flowratem3/hr

22.5 29.3 Min Min

H2O wt% 7 7 7 7

H2S wt% 53 28 - -

RSH wt% - 5 - -

Fuel Gas wt% 40 60 93 93

In normal condition, NH3 rich off gas (from SWS, unit 18) andCNU Off gas (from unit 20) are used as support fuel to achieve750C inside the incinerator combustion chamber.

1.2.2.3. Designed Feed Composition and Capacity for Production of DegassedLiquid Sulphur

The design feed rate of ARU off gas and H2S rich off gas is proportionallyincreased from the given feed stock (Refer to section 1.2.2.1) to get 5ton/day produced degassed liquid sulphur.


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1.2.2.3.1. ARU Off Gas FeedStock Specifications


Composition kg/hr kg-mol/hr Mol% kg/hr kg-mol/hr Mol%H2S 129.6 3.802 18.97 164.2 4.818 20.66

NH3 0.0 0.00 0.00 0.0 0.00 0.00

H2O 20.8 1.157 5.77 26.1 1.448 6.21

Cyanide 0.0 0.00 0.00 0.0 0.00 0.00

CO2 645.9 14.676 73.24 729.6 16.578 71.11

N2 1.3 0,045 0.23 1.4 0.049 0.21

CO 0.1 0.005 0.02 0.1 0.005 0.02

H2 0.4 0.188 0.94 0.4 0.202 0.87C1 1.8 0.110 0.55 2.2 0.137 0.59

C2 1.1 0.04 0.23 1.1 0.04 0.22

C3 1.4 0.046 0.23 1.5 0.050 0.22

Total 801 20.040 100.00 926.6 23.312 100.00

1.2.2.3.2. SWS H2S Rich Off Gas Feedstock Specifications



H2S 103.6 3.039 88.94 69.0 2.026 88.09

NH3 0.0 0.00 0.00 0.0 0.00 0.00

H2O 6.1 0.340 9.96 4.2 0.235 10.21

Cyanide 1.0 0.038 1.10 1.1 0.039 1.70

CO2 0.0 0.00 0.00 0.0 0.00 0.00

N2 0.0 0.00 0.00 0.0 0.00 0.00

CO 0.0 0.00 0.00 0.0 0.00 0.00

H2 0.0 0.00 0.00 0.0 0.00 0.00

C1 0.0 0.00 0.00 0.0 0.00 0.00

C2 0.0 0.00 0.00 0.0 0.00 0.00

C3 0.0 0.00 0.00 0.0 0.00 0.00

Total 110.7 3.416 100.00 74.3 2.300 100.00


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1.2.3. Product Specifications

1.2.3.1. Degassed Liquid Sulphur Specifications

Component Specification

Purity (as S) (wt %) 99.9 (dry basis)

Organics (wt %) 0.02 (dry basis)

Ashes (wt %) 0.04 (dry basis)

Water (wt %) 0.10

H2S content (wt.ppm) 10

Colour Bright Yellow

1.2.3.2. Emissions from Incinerator

The emissions to the atmosphere from the incinerator must not exceedthe following limits as per the requirements of the Vietnamese Air QualityStandard TCVN 5939 1995:

Component Limit

SO2(mg/m3) 500 max (dry basis)

H2S (mg/m3) 2 max (dry basis)

NOX (mg/m3) 1000 max (dry basis)

CO (mg/m3) 500 max (dry basis)

Particulate in Smoke (mg/m3) 400 (dry basis)

Dust containing silica (mg/m3) 50 (dry basis)

Ammonia (mg/m3) 100 (dry basis)

The above specifications are only applicable in normal operation and notin bypass condition).

1.2.4. Utility/Power/Chemicals/Catalyst consumption

1.2.4.1. Utility Consumption

The following describes the utility consumption of the SRU based on theEstimated Utility Consumption Document:

8474L-022-CN-0003-001 Design Case Bach Ho

Note:

In the following subsections EXCEPT ELECTRICAL POWER:


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( ): Intermittent Producer/Consumer

+: Indicates Quantity Produced

-: Indicates Quantity Consumed

1.2.4.1.1. Electrical Power

Item No. Description

Electrical Power (kW)

Service

Duty

UsageFactor

RatedPower

Mech.Absorbed

NormalPower

ConsumedNormalActivePower

BM-2203AMotor for Dilution AirBlower

200.0 148.00 155.60 N C 1

BM-2203B Motor for Dilution AirBlower

200.0 148.00 155.60 N S 0

A-2201-BM-01A

Motor for combustion airblower

22.00 17.00 18.10 N C 1

A-2201-BM-01AA

Motor for canopy fan 0.75 0.60 0.60 N C 1

A-2201-BM-01B

Motor for combustion airblower

22.00 17.00 18.10 N S 0

A-2201-BM-01BA

Motor for canopy fan 0.75 0.60 0.60 N S 0

A-2201-BM-02A

Motor for incinerationcombustion air blower

30.00 18.20 19.40 N C 1

A-2201-BM-02B

Motor for incinerationcombustion air blower

30.00 18.20 19.40 N C 0

A-2201-BM-02A

Motor for incineratorcombustion air blower

45.00 32.00 34.00 N C 1

A-2201-BM-02B

Motor for incineratorcombustion air blower

45.00 32.00 34.00 N S 0

A-2201-PM-

01A

Motor for ARU off gas

KO drum pump

1.50 1.40 1.50 N C 1

A-2201-PM-01B

Motor for ARU off gasKO drum pump

1.50 1.40 1.50 N S 0

A-2201-PM-02A

Motor for H2S rich SWSoff gas KO drum pump

1.50 1.40 1.50 N I 0.1

A-2201-PM-02B

Motor for H2S rich SWSoff gas KO drum pump

1.50 1.40 1.50 N S 0

A-2201-PM-03A

Motor for NH3 rich SWSoff gas KO drum pump

1.50 1.40 1.50 N I 0.1


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Item No. Description

Electrical Power (kW)

Service

Duty

Us

ageFactor

RatedPower

Mech.Absorbed

Normal

Power

ConsumedNormalActive

Power

A-2201-PM-03B

Motor for NH3 rich SWSoff gas KO drum pump

1.50 1.40 1.50 N S 0

A-2201-PM-04A

Motor for sulphurcirculation pump

3.00 3.00 3.20 N I 0.1

A-2201-PM-04B

Motor for sulphurcirculation pump

3.00 3.00 3.20 N S 0

A-2201-PM-05A

Motor for Sulphur Pump 5.50 5.50 5.90 N I 0.1

A-2201-PM-05B Motor for Sulphur Pump 5.50 5.50 5.90 N S 0

WS-2201Welding Socket 1 (unit22)

63.00 63.00 37.10 N S 0

1.2.4.1.2. Steam, Condensate & Boiler Feed Water

Item No.Description

Steam (T/h) Condensate (T/h)BFW(T/h) Losses

(T/h)HPSTM

MPSTM

LPSTM

HPcond

MPcond

LPcond

LPBFW

A-2201 SRU Package -0.3 -0.1 0.4 0.3 0.1 0.25 -0.8 0.15

A-22011ststart-up &prior to shutdown

(-0.4) (-0.1) (-0.4) (0.4) (0.1) (0.25) (0.15)

1.2.4.1.3. Cooling Water & Fresh Water

Item No. Description Cooling Water (m3/h) Fresh Water (T/h)

A-2201 SRU Package -3.2 -0.2

A-2201 Start-up & shutdown (-3.7) -(2.0)


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1.2.4.1.4. Instrument & Plant Air

Item No. DescriptionInstrument

Air (Nm3/h)

Plant Air (Nm3/h)

Continuous IntermittentA-2201 SRU Package -103.4 -400.0

A-2201 Start-up & shutdown [1] (-161.6)

Note:

[1]: Instrument air consumption is in the extreme case where allcontrol valves and on/off valves act together.

1.2.4.1.5. Nitrogen

Item No. DescriptionNitrogen Nm3/h

Continuous Intermittent

A-2201 SRU Package -26.0

A-2201 Start-up & shutdown -138.0

1.2.4.1.6. Furnace & Boilers

Item No. DescriptionFurnace & Boilers

Fuel Fired (MW)

A-2201 SRU Package -0.1

A-2201 Start-up & shutdown (-1.4)

Pilot Gas -0.1

1.2.4.2. Catalysts & Chemicals

The catalyst used in the Claus Catalytic Reactors is Alumina-Titanium for1stReactor and only Alumina for 2ndand 3rdReactors. The Claus catalystis easily available on the market, from Euro Support or Axens forinstance.

Claus reactors catalyst is supported on a layer of catalyst support with aremarkable activity towards the Claus reaction.

The temperature of structural change of the catalyst is above 550 C (farfrom the operating conditions of normal run and during plant heat-up).

Catalyst is very resistant to plant upset (the only exception is the pluggingby soot), but the following phenomena may decrease the activity:


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Thermal and Hydrothermal Ageing

Sulphate Poisoning

In present case Euro Support has been chosen as preferred supplier. Thetrade names are S-2001 for Alumina-based Catalyst, S-7001 for TitaniumOxide Catalyst and 1/2" Ceramic Balls as active catalyst support.

Catalyst

Item Description Catalyst Volume to be loaded (m3)

A-2201-R-02 1streactorAlumina-based catalyst 0.94

Titanium oxide catalyst 0.94

A-2201-R-03 2ndreactor Alumina-based catalyst 1.32

A-2201-R-04 3rdreactor Alumina-based catalyst 1.88

Catalyst Bed Support

Item Description Volume to be loaded (m3)

A-2201-R-02 1streactor 0.28

A-2201-R-03 2ndreactor 0.20

A-2201-R-04 3rdreactor 0.28

When the SRU is processing a feed with the design feed quality, the

Claus catalyst life shall be minimum 2 years.


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1.3. Glossary of terms and Acronyms

1.3.1. Acronyms

COMPANIES/ORGANISATIONS

DQR Dung Quat Refinery

DQIZMBDung Quat Industrial ZoneManagement Board

EVN Electricity Authority of VietnamFW Foster Wheeler Energy LimitedMOC Ministry of Construction

MOSTEMinistry of Science, Technologyand Environment

MPIMinistry of Planning andInvestment

SRV Socialist Republic of VietnamTPC Technip Consortium

OTHERS

ACE Application Control Environment MC Marshalling Cabinet

ADASAnalyser Data AcquisitionSystem

MCB Main Control Building

ADP Alarm Display Panel MCC Motor Control CenterAER Application Engineers Room MCR Main Control Room

AI Analyser Indicator

MCSMOVControlSystem

MOV Control System

AIT Auto Ignition Temperature MDF Main Distribution Frame

AMS Asset Management System MISManagement InformationSystem

ANSIAmerican National Standardsinstitute

MMS Machine Monitoring System

APC Advanced Process Control MMTMinimum MaintainedTemperature

API American Petroleum Institute MOC Madrid Operating CenterARU Amine Regeneration Unit MOM Minutes of Meeting

ASC Analyser Speciality Contractor MOV Motor Operated ValveASME

American Society ofMechanical Engineers

MP Medium Pressure

ASP Analyser Systems Package MPTMinimum PressurizationTemperature

ASTMAmerican Society of Testingand Materials

MR Material Requisition

ATM Asynchronous Transfer Mode MRR Marshalling Rack RoomBCS Blending Control System MSD Material Selection DiagramBEDD Basic Engineering Design Data MSDS Material Safety Data SheetBFD Block Flow Diagram MTBF Mean Time Between FailuresBFW Boiler Feed Water MTTR Mean Time To Repair


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BL Battery Unit MTO Material Take-OffBOM Bill of Materials MTPA Metric Tonnes per Annum

BPC Blending Properties Control MVIPMulti Vendor InterfaceProgram (Honeywell)

BPCD Barrels per Calendar Day NACENational Association ofCorrosion Engineers

BPSD Barrels per Stream Day NCR Non Conformance ReportBRC Blending Ratio Control NDE Non Destructive Examination

CAD Computer Aid Design NFPANational Fire ProtectionAssociation

CALM Catenary Anchor Leg Mooring NHT Naphtha Hydrotreater (Unit)CBT Commercial Bid Tabulation NIR Near Infrared Spectroscopy

CCARControl Complex AuxiliaryRoom

NPSH Net Positive Suction Head

CCC Central Control Complex NPV Net Present ValueCCR Continuous Catalytic Reformer NTU Naphtha Treater Unit

CCTV Closed Circuit Television OAS Oil Accounting SystemCD Chart Datum OJT On Job Training

CDU Crude Distillation Unit OM&SOil Movement and StorageControl System

CENELECEuropean Committee forElectrotechnical Standardization

OMSAOil Movement and Storageautomation

CFC Chlorofluorocarbons OOS Operation Override Switch

CFRCooperative Fuel Research(Engine)

OPSSOperations Planning andScheduling System

C&I Control and Instrumentation OSBL Outside Battery Limit

CMMSComputerized MaintenanceManagement System

OTS Operator Training Simulator

CNU (Spent) Caustic NeutralizationUnit

PABX Private Automatic BranchExchange

CPI Corrugated Plate Interceptor PAGAPublic Address / GeneralAlarm

CSI Control Systems Integrator PCB Printed Circuit BoardDAF Dissolved Air Flotation PFD Process Flow DiagramDAU Data Acquisition Unit PFM Path Find ModuleDCS Distributed Control System PDB Project Documents Base

DEA Diethanolamine PGCProcess Gas Chromatograph(Analysers)

DEIADetailed Environmental ImpactAssessment

PHD Plant History Database

DMDS Dimethyldisulfide PI Plant AirDMS Document Management System PIB Process Interface Building

DNV Det Nork Veritas PIDPiping and InstrumentDiagram

DPTDDesign, Pressure, TemperatureDiagram

PIMProject ImplementationManual

DQMISDung Quat ManagementInformation System

PKSProcess Knowledge System(Honeywell DCS)

DQRP Dung Quat Refinery Project PLEM Pipeline End ManifoldDVM Digital Video Manager PLG PlanningDWT Dead Weight Tonnes PMC Project Management


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ConsultantEL Equipment List PMI Positive Material IdentificationEOR End of Run PMT Project Management Team

EDMSElectronic DocumentManagement System

PO Purchase Order

EMC Electromagnetic Compatibility POC Paris Operating Center

EPCEngineering Procurement,Construction andCommissioning

PP Project Procedure

ERP Enterprise Resource Planning PPB Parts per BillionES Ethernet Switch PPM Parts per MillionESD Emergency Shut Down PRU Propylene Recovery UnitETP Effluent Treatment Plant PWHT Post Weld Heat TreatmentETS Effluent Treatment System QA Quality AssuranceEWS Engineering Work Station QC Quality ControlFDC Feed Development Contract RA Risk Analysis

FAP Fire Alarm Panel R&D Research and DevelopmentFAT Factory Acceptance Test RDBMS

Real Time DatabaseManagement System

FEL Front End Loading RFCCResidue Fluid CatalyticCracking

F&G Fire and Gas System RFSU Ready for Start-UpFIU Field Interface Unit RLU Remote Line UnitFIC Flow Indicating Controller ROW Right of Way

FM Factory Mutual (Approval body) RPMSRefinery PerformanceManagement System

FOTC Fibre Optic Termination Cabinet RTDResistance TemperatureDetector

FSC Fail Safe Controller (HoneywellESD)

RTDB Real Time Data Base(System)

FTE Fault Tolerant Ethernet RTU Remote Terminal UnitGC Gas Chromatograph SAT Site Acceptance TestGFT Ground Fault SBT Segregated Ballast Tanks

HAZAN Hazard Analysis Study SBMSSoftware Bypass ManagementSystem

HAZOP Hazard and Operability Study SCADASupervisory Control and DataAcquisition

HDT Hydrotreater SCC Satellite Control Complex

HEI Heat Exchange Institution SCESimulation ControlEnvironment

HHP High High Pressure (Steam) SCR Satellite Control RoomHGO Heavy Gas Oil SDH Synchronous Digital HierarchyHIC Hydrogen Induced Cracking SE Safety EarthHP High Pressure S&E Safety & EnvironmentalHSE Health, Safety and Environment SGS Safeguarding System

HVACHeating Ventilation AirConditioning

SOE Sequence of Events

IA Instrument Air SOR Start of Run

ICAOInternational Civil AviationOrganisation

SOW Scope of Work

ICE Instrument Clean Earth SP Specification


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ICS Integrated Control System SPIRSpare Parts andinterchangeability Record

IIP Initial Interface Plan SPM Single Point MooringI/O Input/Output SR Scope of SupplyIP Institute of Petroleum SRU Sulphur Recovery Unit

IPSInstrumented ProtectiveSystem

STC Construction Standard

IRP Interposing Relay Panel STD Design StandardIRR Internal Rate of Return STEL Short Term Exposure Limit

IS Intrinsically Safe SVACShelter Ventilation and AirConditioning

ISA Instrument Society of America System (Analyser houses)ISE Intrinsically Safe Earth SWS Sour Water Stripping (Unit)ISBL Inside Battery Limit TAS Terminal Automation SystemISOM Isomerisation Unit TBT Technical Bid Tabulation

ITB Invitation to Bid TCFTemporary Construction

FacilitiesITP Inspection and Test Plan TCM Task Control Module

JB Junction Box TEMATubular ExchangerManufacturers' Association

JCC Jetty Control Complex TGIFTemperature Gauge IndicationFacilities (Tankage)

JCR Jetty Control Room TLCR Truck Loading Control RoomJSD Job Specification for Design TLCS Truck Loading Control SystemJSS Job Specification for Supply TN Transmittal Note

JVD Joint Venture Directorate TPSTotal Plant Solution(Honeywell)

KLOC Kuala Lumpur Operating Center TQM Total Quality Management

KTU Kerosene Treatment Unit TS Terminal ServerLAN Local Area Network TWA Time Weighted AverageLCO Light Cycle Oil UFD Utility Flow diagramLCOHDT LCO Hydrotreater U/G Underground

LDE Lead Discipline Engineer ULUnderwriter Laboratories(Approval body)

LELLower Exposition Limit (F&G,Analysers)

UPS Uninterruptible Power Supply

LGO Light Gas Oil VDU Visual Display Unit

LIMSLaboratory InformationManagement System

VPU Vendor Package Unit

LIS Laboratory Information System WABT

Weight Average Bed

TemperatureLLU Local Line Unit WBS Wash Breakdown StructureLP Low Pressure WHB Waste Heat BoilerLPG Liquefied Petroleum Gas YOC Yokohama Operating CenterLTU LPG Treater Unit

1.3.2. Glossary

Refer to separate glossary.


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TRAINING MODULE


UNIT: 22

Course Content:


Section 2 - Process Flow Description XSection 3 - Process Control

Section 4 - Safeguarding Devices



Section 7 - Cause & Effects

Section 8 - Operating Procedures

Section 9 - HSE



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SECTION 2 : PROCESS FLOW DESCRIPTION

Figure 4: SRU Block Flow Diagram


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Figure5:SRUSimp

lifiedProcessFlow

Diagram


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2.1. Claus Section

2.1.1. ARU Off Gas from Unit 19 & H2S Rich Off Gas from Unit 18

The ARU Off Gas (from Unit 19) and the H2S Rich Off gas (from Unit 18) are fed

to 2 dedicated KO drums (A-2201-D-01 & A-2201-D-02), provided with misteliminators, in order to separate acid condensate and all liquid carry-over comingfrom upstream units. Indeed liquid carry-over is very dangerous to the life ofdownstream equipment and to the correctness of operation.

2 dedicated pumps, A-2201-P-01 A/B & A-2201-P-02 A/B, send acid condensatecollected in A-2201-D-01 & A-2201-D-02 respectively to closed drain drum in unit19 and unit 18 respectively. The pumps operate on level control of their respectiveKO drum.

ARU Off gas from KO drum A-2201-D-01 is heated against HP superheated steamin the ARU off gas preheater A-2201-E-01. The steam is fed to A-2201-E-01 ontemperature control of the ARU off gas at the discharge of the preheater. ARU off

gas is then fed to the burner of the thermal reactor A-2201-R-01 on flow controlreset by PIC-529 at the off gas outlet of A-2201-D-01. Part of the ARU off gas isnot fed to the thermal reactor burner but flows straight to the 2nd zone of thereactor.

After being mixed with the off gas from A-2201-D-01 downstream of the ARU offgas preheater A-2201-E-01, H2S rich SWS off gas from KO drum A-2201-D-02 isfed to the burner of the thermal reactor A-2201-R-01 on flow control reset by PIC-530 at the off gas outlet of A-2201-D-02..

Condensation in the separator downstream line is prevented by low pressuresteam tracing.

In case of the Claus section is temporarily out of operation, the ARU Off Gas andthe H2S Rich Off Gas are bypassed to the Incinerator (A-2201-H-01) via dedicatedlines from each K.O. drum.

2.1.2. Combustion air feeding to Claus section

Air required for acid gases combustion is compressed in the Combustion AirBlower A-2201-B-01 A/B. The compressed air pressure at the blowers dischargeis controlled by PIC-545 which vent excess air to atmosphere.

A small fraction of the compressed air is used to strip H2S from produced sulphur,inside the Liquid Sulphur Degassing Pit (A-2201 -TK-01).

Once compressed, combustion air is preheated in the Combustion Air PreheaterA-2201-E-02 against HP superheated steam in order to increase as much aspossible the adiabatic flame temperature in Thermal Reactor (A-2201-R-01). Theflow of steam to the preheater is temperature controlled by TIC-523 measuring thetemperature of the heated air at A-2201-E-02 discharge.

Then combustion air is fed to the burner of the thermal reactor A-2201-R-01.


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2.1.3. Thermal Reactor and Burner

Thermal Reactor (A-2201-R-01) and relevant burner are the most important itemsin the Claus section and correct operation in that area is mandatory to assuresmooth run.

Combustion of acid gases is done under highly controlled condition, in order toassure proper air feeding and, as a result, proper run conditions. All acid streamflow rates are corrected for pressure and temperature and are controlled keepingthe header pressure at the constant value. Combustion air is managed in order toassure proper flow rate.

The air fed to the main burner is exactly sufficient to accomplish the completeoxidation of hydrocarbons and all the impurities (such as HCN) present in the totalfeed gases and to burn approximately one-third of the total H2S to SO2maximizing the overall sulphur recovery efficiency.

Burner is provided with a fuel gas gun and ancillaries to burn refinery fuel gas inheating up conditions, when the unit is too cold to accept acid gas in safeconditions. Fuel gas line is equipped with flow control system and shut downvalves. Air flow rate required for proper combustion is fed via ratio control, usingsame criteria as for acid gas feeding.

The Thermal Reactor (A-2201-R-01) is a 2 zones reaction furnace, each zoneoperating at different temperature:

In the 1st zone all combustion air, all H2S Rich Off gas and a fraction ofARU Off Gas are burnt.

Combustion air flow rate present in flame area is relatively higher than therequired for Claus reactions, due to the by-pass of the part of ARU Off Gasflow rate to the second zone. The resulting flame temperature is higher thanexpected (regarding standard Claus reactions only) and in this way isguaranteed flame stability and complete hydrocarbon and impuritiescombustion.

In the 2ndzone the hot flue gas from the first zone and the remaining ARUOff Gas are mixed. As the remaining ARU Off Gas is injected, temperatureis lowered and modifications in flue gas composition take place in order tosatisfy the overall heat and material balances.

Optimum temperature is achieved by-passing about 50% of ARU Off Gas to thesecond zone at design flowrate.

The flue gas leaving then leaves the reactor and enters into the Claus Waste HeatBoiler and Sulphur Condensers A-2201-SG-01.

The temperature inside the first zone is approx. 1240C and the temperature offlue gas leaving the reactor is approx. 900C.

The expected overall conversion of H2S to sulphur in the Thermal Reactor (A-2201-R-01) is approx. 16.4% at design conditions (Max. Gasoline Case).


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2.1.4. Claus Waste Heat Boiler and 1stSulphur Condenser

The Claus Waste Heat Boiler & Sulphur Condensers A-2201-SG-01 is a 5 passesboiler producing saturated low pressure steam at 4.1 kg/cm2G:

pass I = 1stpass of WHB

pass II = 2ndpass of WHB

pass III = 1stsulphur condenser

pass IV = 2ndsulphur condenser

pass V = 3rdsulphur condenser

LP steam is generated shell side and delivered to the LP steam header. Producedsteam is controlled at 4.1 kg/cm2G by pressure controller PIC-555.

Boiler feed water is fed to the A-2201-SG-01 under level control of A-2201-SG-01

by LIC-514.A-2201-SG-01 is equipped with the Claus Blow Down Cooler (A-2201-D-06), onwhich service water is used in open circuit to cool the water blown down from A-2201-SG-01. The water blown down is then discharged into oily surface watersewer at a maximum temperature of 50C.

The combustion products leaving the Thermal Reactor A-2201-R-01 are sent intothe tubes and are cooled down to about 240C in pas ses I & II of the Claus WasteHeat Boiler.

The process gas leaving the Claus Waste Heat Boiler is further cooled down to

about 162C in the 1st

Sulphur Condenser (A-2201-SG-01 pass III). The sulphurproduced in the A-2201-R-01 is condensed in the tube side of A-2201-SG-01 passIII and discharged by gravity to the sulphur pit (A-2201-TK-02) through itsdedicated sulphur seal leg (A-2201-D-05 A).

2.1.5. 1stProcess Gas Reheater & 1stCatalytic Reactor

The process gas leaving the 1st Sulphur Condenser (A-2201-SG-01) pass III isheated up to 240C in the 1 stProcess Gas Reheater (A-2201-E-03), by means ofsuperheated HP steam fed under temperature control by TIC-541 of the processgas leaving the reheater, prior to being sent to the 1stCatalytic Reactor (A-2201-

R-02).

The process gas enters the A-2201-R-02 where the Claus reaction between H2Sand SO2 continues until equilibrium is reached at that condition, producingelemental Sulphur.

Equilibrium temperature is approximately the temperature of process gas leavingthe reactor (A-2201-R-02), i.e. 321C at design con ditions (Max. Gasoline Case).


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2.1.6. 2ndCondenser, 2ndProcess Gas Reheater & 2ndCatalytic Reactor

The process gas leaving the 1stCatalytic Reactor (A-2201-R-02) is fed to the 2ndSulphur Condenser (A-2201-SG-01 pass IV). The sulphur produced in the A-2201-R-02 is condensed in the tube side of A-2201-SG-01 pass IV and discharged by

gravity to the Sulphur Pit (A-2201-TK-02) through its dedicated sulphur seal leg(A-2201-D-05B).

A mist eliminator device is provided on the outlet channel of the A-2201-SG-01pass IV to remove the sulphur entrained as mist in the process gas.

The process gas leaving 2ndSulphur Condenser (A-2201-SG-01 pass IV) at 170Cis fed to the 2ndProcess Gas Reheater (A-2201-E-04) to be heated up to 205C bymeans of superheated HP steam fed under temperature control by TIC-539 of theprocess gas leaving the reheater. The process gas then enters the 2nd CatalyticReactor (A-2201-R-03) where the Claus reaction between H2S and SO2continues until equilibrium is reached at these conditions, producing elementalSulphur.

Equilibrium temperature is approximately 223C at d esign conditions (Max.Gasoline Case).

2.1.7. 3rdCondenser, 3rdProcess Gas Reheater & 3rdCatalytic Reactor

The process gas leaving the 2nd Catalytic Reactor (A-2201-R-03) is fed to the 3rdSulphur Condenser (A-2201-SG-01 pass V). The sulphur produced in the A-2201-R-03 is condensed in the tube side of A-2201-SG-01 pass V and discharged bygravity to the Sulphur Pit (A-2201-TK-02) through its dedicated sulphur seal leg(A-2201-D-05C).

A mist eliminator device is provided on the outlet channel of the A-2201-SG-01pass V to remove the sulphur entrained as mist in the process gas.

The process gas leaving the 3rd Sulphur Condenser (A-2201-SG-01 pass V) at162C is fed to the 3 rdProcess Gas Reheater (A-2201-E-05) to be heated up to190C by means of superheated HP steam fed under te mperature control by TIC-540 of the process gas leaving the reheater. Heated process gas then enters the3rdCatalytic Reactor (A-2201-R-04) where the Claus reaction between H2S andSO2 continues until equilibrium is reached under these conditions, producingSulphur.

Equilibrium temperature is approximately 193C at d esign conditions (Max.Gasoline Case).

The .following DCS printout shows the catalytic reactors:


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2.1.8. Final Sulphur Condenser and Tail Gas Coalescer

The process gas leaving the 3rdCatalytic Reactor (A-2201-R-04) at 193C is fed tothe tube side of the Final Sulphur Condenser (A-2201-E-06) for the final coolingagainst boiler feed water (shell side), to recover sulphur produced in the A-2201-

R-04.Cooling down has been maximized to decrease to the minimum the sulphurpresent as elemental sulphur in the tail gas.

The sulphur produced is condensed in the tube side of A-2201-E-06 anddischarged by gravity to the Sulphur Pit (A-2201-TK-02) through its dedicatedsulphur seal leg (A-2201-D-05D).

The sensible heat of the process gas entering the Final Sulphur Condenser (A-2201-E-06) vaporizes the BFW coming from the Steam Condenser (A-2201-E-07).

Produced steam is pressure controlled at 1 kg/cm2G (120C) by PIC-562 on theA-2201-E-06 outlet line to the steam condenser, in order to ensure that in all

operating conditions, the tube temperature of A-2201-E-06 is always higher thanfreezing point of sulphur, avoiding operating problems, but still as low as possible.

Steam fed to A-2201-E-07 is condensed against cooling water before beingreturned to the final sulphur condenser.

For warm-up or turndown operations, to avoid sulphur solidification, LP Steam issend to the shell of the Final Sulphur Condenser (A-2201-E-06) via a dedicatedsparger.

The process gas coming from the A-2201-E-06 is fed to the Tail Gas Coalescer(A-2201-D-04) to remove any sulphur mist from the process gas. Condensedliquid elemental sulphur is then sent by gravity to the Sulphur Pit (A-2201-TK-02)via sulphur seal leg (A-2201-D-05D).

The tail gas leaving the Sulphur Coalescer (A-2201-D-04), at approx. 130C, is feddirectly to the Incinerator (A-2201-H-01).

2.2. Liquid Sulphur Storage Pit

The elemental liquid sulphur condensed in the 4 condensation steps is discharged bygravity to the Liquid Sulphur Storage Pit (A-2201-TK-02) through the sulphur seal legs(A-2201-D-05A/B/C/D).

Each sulphur seal leg has been provided with dedicated filter (perforated plate type) toavoid plugging by catalyst and refractory dust. Sulphur seal legs are fully steam jacketed

and sized to avoid blow up of process gas in all operating conditions, also in case ofheavy upset.

Note that each sulphur seal leg has a dedicated manual, steam jacketed valve, to isolatethe items in case of scheduled maintenance and during the dry out operations. In noother conditions the valve should be closed.

Sulphur pit is divided in two different sections, a non-degassed sulphur pit and adegassed sulphur storage pit:

The non-degassed sulphur storage section, sized for about one day of productionof Claus section, is equipped with 2 fully steam jacketed sulphur pumps (A-2201-P-04 A/B).


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A-2201-P-04 A/B transfer continuously the produced sulphur to the Liquid SulphurDegassing Pit (A-2201-TK-01).

The degassed sulphur storage section is sized for about one day of production ofClaus section and is equipped with two fully steam jacketed sulphur pumps (A-

2201-P-05 A/B) that transfer the degassed sulphur to the Sulphur Apron.Sulphur pit operates under approx. -50 mmH2O (G). Air intake is sucked from A-2201-TK-01 by the Pit ejector (A-2201-J-01 A/B) which is fully steam jacketed. Air is thendischarged to the Incinerator (A-2201-H-01).

2.3. Sulphur Degassing Section

Liquid sulphur leaving the Claus section may cause environmental and safety problemsdue to the presence of H2S, which is partly physically dissolved and partly present in theform of polysulphides (H2Sx).

On the average, liquid sulphur contains 250-300 wt.ppm H2S. During the transport andstorage the H2S will be released from the sulphur resulting in the creation of an explosivemixture if the lower explosion limit of H2S in air exceeded. This limit ranges between 3.7vol% H2S at 130C and 4.3 vol% H2S at ambient tempe rature.

The sulphur degassing process is used to strip liquid sulphur down to 10 wt.ppmH2S/H2SX, which is the safe level top avoid exceeding of the lower explosion limit.

For this, process air from A-2201-B-01A/B is bubbled through the sulphur to decomposethe polysulphides and to release the physically dissolved H2S, without chemicalsaddition. The degassing is carried out in the Liquid Sulphur Degassing Pit (A-2201-TK-01) provided with suitable perforated plates to allow contact between not degassedsulphur and stripping air.

The air bubbling through the sulphur decreases the partial pressure of H2S and inducesa vigorous agitation. Consequently a good contact between liquid sulphur and oxygen isobtained, which accelerates the decomposition of polysulphides into H2S and S, stripsthe dissolved H2S from the sulphur and oxidises a part of H2S to sulphur.

An additional amount of air (sweep air) is drawn into the Liquid Sulphur Storage Pit (A-2201-TK-02) to ventilate the vapour space above the sulphur level and to keep theH2Sconcentration below its lower explosion limit.

The stripped H2S is removed by the steam ejector (A-2201-J-01A/B) and sent to theIncinerator (A-2201-H-01).

Degassed elemental sulphur then flows to the degassed sulphur storage section before

being pumped by A-2201-P-05 A/B to the sulphur apron.

The following DCS printout shows the sulphur storage pit and degassing section:


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2.4. Incinerator Section

The tail gas leaving the Claus section, as well as vent air from ejectors, are fed to theIncinerator (A-2201-H-01) to burn the residual H2S. In order to meet the requirements onthe flue gas delivered to the atmosphere, dilution air from Dilution Air Blower (B-2203

A/B) is fed to the Stack.In normal condition NH3 Rich Off gas (from Unit 18) and CNU Off gas (from Unit 20) areused as support fuel to achieve 750C inside the co mbustion chamber. A refinery fuelgas is used to guarantee the maintenance of the required temperature in case of NH3Rich Off gas and/or CNU Off gas flowrate fluctuations.

NH3 rich SWS off gas is fed to the NH3 Rich Off Gas KO Drum A-2201-D-03, providedwith mist eliminator in order to separate NH3 condensate and all liquid carry-over comingfrom NH3. The NH3 Rich Off Gas KO Drum Pumps A-2201-P-03 send any condensatecollected in A-2201-D-03 back to the closed drain drum in SWS unit. The pumps operateon level control of A-2201-D-03.

The separated off gas from A-2201-D-03 is then sent to the combustion chamber of theincinerator A-2201-H-01.

NH3 Rich Off gas and/or CNU Off gas or support fuel gas are burnt with combustion airfrom the Incinerator Combustion Air Blower (A-2201-B-02A/B), operating at relativelyhigh air excess in order to achieve optimum flame temperature.

The Claus tail gas and the vent gas from pit ejectors (A-2201-J-01 A/B) are mixed withhot flue gas, at controlled temperature, and all sulphur bearing compounds are oxidisedto SO2.

Expected residual H2S content is lower than 10 vol.ppm.

The combustion air is supplied by the Incinerator Combustion Air Blower (A-2201-B-02A/B) and controlled as a ratio to the NH3 Rich Off gas, CNU Off gas and refinery fuel gasflow.

If the Claus section is not in operation, all the ARU Off Gas and H2S Rich Off gas aresent to the Incinerator Burner.

2.5. DCS Printouts SRU Process Overview

The following DCS printouts show the overview of the SRU process:


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TRAINING MODULE


UNIT: 22

Course Content:


Section 2 - Process Flow Description

Section 3 - Process Control XSection 4 - Safeguarding Devices



Section 7 - Cause & EffectsSection 8 - Operating Procedures

Section 9 - HSE



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SECTION 3 : PROCESS CONTROL

The following is a description of the main control loops of the SRU. For a detailed description of

the control loops and the controllers, refer to the control narrative, vendor document No. 8474L-022-A3505-4110-300-003.

3.1. Control narrative & operating parameters

3.1.1. ARU Off Gas KO Drum A-2201-D-01 Pressure Control

This control system acts in order to maintain a stable pressure in the ARU off gasKO drum feeding the thermal reactor when the SRU is in normal operation mode(or the incinerator when the SRU is in bypass mode).

The pressure in A-2201-D-01 is controlled by 022-PIC-529 acting in split rangecontrol on 2 control valves:

022-PV-529 controlling the ARU gas flow to the incinerator A-2201-H-01

022-FV-530 controlling the ARU gas flow to the thermal reactor A-2201-R-01. In that case, PIC-529 is in cascade with FIC-530

In case of a pressure increase measured by PT-529 at the outlet of A-2201-D-01,PIC-529 will 1stopen the FV-530 by resetting the setpoint of FIC-530 via PY-529A,while PV-529 will remain close. This is the low range case (0-50%).

If the pressure continue to increase (high range: 50-100%), then PIC-529 will openPV-529 via PY-529B, while FV-530 remains open.


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Figure 6: A-2201-D-01 Pressure Control

Since in normal operation, the ARU off gas line to the incinerator is closed by acut-off valve 022-XV-516, the action of PV-529 valve opening has no effect inmitigating the pressure increase. Therefore, the ARU off gas will be flared to the

sour flare by the control valve on the upstream unit (i.e.: Amine Regeneration).In the same manner, during SRU bypass operation, the ARU off gas line to theThermal Reactor is closed by a cut-off valve 022-XV-505, therefore the action of022-FV-530 valve opening has no effect in mitigating the pressure increase andthe ARU off gas will be flared to the sour flare header by the control valve on theupstream (i.e.: Amine Regeneration).

There is only one operating mode during which both cut off valves are opened:This is when the plant is in bypass mode with the incinerator receiving acid gasesand the SRU is to be re-started with acid gases. In this case, FV-530 is operated


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in manual mode (gradual opening) by acting directly on the controller FIC-530.This cause a pressure decrease and PIC-529 controller output acts by closinggradually PV-529 up to complete closure.

This way, gradual acid gas cut-in to the thermal reactor and acid gas cut-off the

incinerator are ensured.

3.1.2. H2S Rich SWS Off Gas KO Drum A-2201-D-02 Pressure Control

The pressure control of A-2201-D-02 is strictly the same than the pressure controlof A-2201-D-01:

This control system acts in order to maintain a stable pressure in the H2S rich offgas KO drum feeding the thermal reactor when the SRU is in normal operationmode (or the incinerator when the SRU is in bypass mode).

The pressure in A-2201-D-02 is controlled by 022-PIC-530 acting in split rangecontrol on 2 control valves:

022-PV-530 controlling the H2S rich off gas flow to the incinerator A-2201-H-01

022-FV-515 controlling the H2S rich off gas flow to the thermal reactor A-2201-R-01. In that case, PIC-530 is in cascade with FIC-515

In case of a pressure increase the controller will first open FV-515 while PV-530will remain close. Then PIC-530 will open PV-530, while FV-530 remains open.


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Figure 7: A-2201-D-02 Pressure Control

Since in normal operation, the H2S rich SWS off gas line to the incinerator isclosed by a cut-off valve 022-XV-516, the action of PV-530 valve opening has noeffect in mitigating the pressure increase. Therefore, H2S rich SWS off gas will be

flared to the sour flare by the control valve on the upstream unit (i.e.: SWS).In the same manner, during SRU bypass operation, the H2S rich SWS off gas lineto the Thermal Reactor is closed by a cut-off valve 022-XV-501, therefore theaction of FV-515 valve opening has no effect in mitigating the pressure increaseand the H2S rich SWS off gas will be flared to the sour flare header by the controlvalve on the SWS.

There is only one operating mode during which both cut off valves are opened:This is when the plant is in bypass mode with the incinerator receiving acid gasesand the SRU is to be re-started with acid gases. In this case, FV-515 is operatedin manual mode (gradual opening) by acting directly on the controller FIC-515.


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This cause a pressure decrease and PIC-530 controller output acts by closinggradually PV-530 up to complete closure.

This way, gradual acid gas cut-in to the thermal reactor and acid gas cut-off theincinerator are ensured.

The following DCS printout shows the ARU off gas KO drum and the H2S richSWS off gas KO drum:


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3.1.3. A-2201-D-01/02/03 Level Control

The level in the KO drums A-2201-D-01/02/03 is controlled by LIC-503/504/505on/off controllers with the starting/stopping of the KO drum pump A-2201-P-01/02/03 A/B, respectively.

The control scheme is the same for these 3 KO drums:

For each of them, the level controller of the KO drum will start the duty pump whenthe level increases to the upper setpoint and will stop the pump when the level inthe KO drum falls to the lower setpoint. For this to be effective, the duty has to beselected in remote (at local selector) and auto operation (on the DCS).

In addition, if pump doesnt start at upper setpoint or doesnt stop at lowersetpoint, High and Low level alarms will be respectively displayed at DCS. Thepumps will also be tripped in case of low low level (refer to section 4 of the presentdocument).

The following DCS printout shows the NH3 rich SWS off gas KO drum:


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3.1.4. Thermal Reactor Combustion Air Control

The task of the Burner Control System is to control the amount of combustion airto the main burner and to provide smooth operation. According to the overalloperation when optimisation of sulphur recovery is the required goal (Claus Mode

operation) the control system ensures that the proper amount of the feed H2S willbe burnt in order to obtain the downstream Claus reaction as complete aspossible.

So, during Claus Mode operation, a too high or too low air flowrate will decreasethe sulphur recovery rate, and once a gas having an incorrect air/gas ratio hasentered the main burner, the resulting conversion loss cannot be compensated.

The correct amount of air is determined by two process variables: the feed gasflowrate and the specific air demand of the feed gas, which depends upon the H2Scontent and the content of other combustible components. The combustion aircontrol system must adjust the air flow according to these two variables.

The feed gas flowrate can vary quite fast; consequently the ratio control part of thesystem must be very fast and accurate.

The variations of the specific air demand are normally much slower. Changes ofthis demand are detected downstream the Claus reactors, by measuring the H2Scontent in the tail gas. If this content shows a deviation from the desired value, theOperator will adjust the desired air/gas ratio.

3.1.4.1. Main Combustion Air Flowrate to Thermal Reactor

The purpose of this control is to maintain correct combustion conditionswithin the Thermal Reactor A-2201-R-01 by ensuring the correct ratio of

combustion air to acid gases or by ensuring the correct ratio ofcombustion air to Fuel Gas during the fuel gas combustion. The controlscheme is a feed-forward air control system based on predetermined feedgases compositions. Variations in acid gases compositions are handledby the feed-back control signal from the tail gas analyzer to the trim aircontrol loop (see next paragraph).

Main combustion air flowrate is controlled by FIC-527 receiving itssetpoint from the combustion control system. FIC-527 setpoint isdetermined by the flowrates of combustible gases in the followingmanner:

Fuel Gas flowrate is measured by FIC-526 and the value is

multiplied by a proper Air/Fuel Gas Ratio in the block FY-554.Air/Fuel Gas Ratio is assigned by a manual setting station HIC-511. The output of the ratio function (or manipulated variable)stands for the air quantity required to burn with a predeterminedratio the Fuel Gas.

H2S Rich Off Gas flowrate to the thermal reactor 1st zone ismeasured by FIC-515 and the signal enters the compensationblock FY-548. Then the compensated H2S Rich Off Gas flowratevalue from FY-548 is multiplied by a proper Air/ H2S Rich Off Gasratio in the FY-549 block. Air/ H2S Rich Off Gas ratio is assignedby a manual setting station HIC-509. The output of the ratio block


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represents the air quantity required in order to burn with apredetermined ratio the H2S Rich Gas.

ARU Off Gas flowrate to the thermal reactor 1stzone is measuredby FIC-530 and the signal enters the compensation flow block FY-

551. ARU Off Gas flowrate to thermal reactor 2nd

zone is measuredby FIC-524 and the signal enters the compensation block FY-522.The 2 compensated ARU Off Gas flowrates values are summed upin FY-558 block, generating as output the total ARU off gasflowrate. This value is then multiplied by a proper Air/ARU off gasratio in the FY-550 block. Air/ARU gas ratio is assigned by amanual setting station 022-HIC-510. The ratio function outputrepresents the air quantity needed in order to burn with apredetermined ratio the ARU Off Gas.

The 3 air flowrate contributions calculated above are summed up inthe FY-553 block and the resulting manipulated variable represents

the total air quantity needed to maintain correct combustionconditions.

The output from FY-553 block is assumed as setpoint for FIC-527 whichregulates the main combustion air flowrate to the thermal reactor with FV-527 accordingly.

In addition, FIC-527 receives a signal from FY-556 compensation block inorder to compensate the flowrate according to the actual conditions.


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Figure8:MainC

ombustionAirFlowrate


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3.1.5. Trim Air Flow to Thermal Reactor Control by Tail Gas Analysis

The purpose of the controller is to control the efficient acid gas conversion withinthe thermal reactor by monitoring the residual levels of H2S and SO2 in the tailgas from the Claus Section.

The trim air flowrate permits to achieve he optimum H2S/SO2ratio of 2:1 in tail gasleaving the Tail Gas Coalescer A-2201-D-04.

The controller acts in feed-back control mode on the trim air control valve FV-022and takes into account small deviations of acid gases composition with respect tothe predetermined one.

Figure 9: Trim Air Flowrate to Thermal Reactor


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Air demand signal is measured by 022-AT-501 and provides set point forcombustion trim air controller FIC-522. The later adjust the trim air flowrate withFV-522 on the trim air line to the thermal reactor.

When the output value of the controller AIC-501 is less than zero, the setpoint of

FIC-522 is increased thereby opening the control valve. When the output value ofthe controller AIC-501 is greater than zero, the setpoint of FIC-522 is decreased,thereby closing the control valve.

022-AY-501 calculates the air demand of the Claus section expressed in terms ofthe stoichiometric air required by the process, that is 2 x [SO2] [H2S]. When theoptimum H2S/SO2content ratio of 2:1 in tail gas is achieved, then the air demandcalculated is zero and no control action is required. When the calculated airdemand is greater than zero (SO2 content 0.5 H2S content in the tail gas) itmeans that there is an excess of air and the controller shall close the controlvalve. Conversely, when the air demand is less than zero, there is deficient air and

the controller shall open the control valve.

The output of trim air controller 022-AIC-501, representing the desired air/gasratio, is a very important signal. Normally it varies between very narrow limits,following the specific air demand of the feed gases. In order to avoid heavyupsets, e.g. as a consequence of H2S analyser malfunctioning, this signal shouldbe limited slightly outside the normal operating range. Outside the expected range,the controller 022-AIC-501 is switched automatically to manual mode and theair/gas ratio control is operated in automatic mode, using the manual output signalas the ratio set points. If required, these set points should be changed very slowlyand carefully.

3.1.6. Quench Steam Flowrate Control

This control is design to gradually increase and maintain correct combustiontemperature within the thermal reactor by feeding steam as a tempering mediumin a suitable ratio to fuel gas.

Quench steam flowrate is controlled by FIC-025 receiving its setpoint from thecombustion control system.

FIC-525 set point is determined by the fuel gas flowrates in the following manner:

Fuel gas flowrate is measured by FIC-526 and the process value is multiplied by aproper Steam/Fuel Gas ratio in the FY-555 block. Steam/Fuel Gas ratio isassigned by a manual input setting station HIC-512. The output of the ratio blockrepresents the steam quantity needed in order to temper the combustiontemperature in the thermal reactor.

The output from 022-FY-555 block is assumed as setpoint for FIC-525 whichregulates the flow of steam to the thermal reactor with FV-525.

The following DCS printouts show the thermal reactor, waste heat boiler andsulphur condenser section:


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3.1.7. Combustion Air to Incinerator Flowrate Control (A-2201-H-01)

The control system is designed to maintain stable and adequate combustionconditions within the incinerator. Combustion air flowrate controller FIC-539setpoint is determined by the flowrates of combustible gases in the following

manner: Fuel Gas flowrate is measured by FI-535 and the value is multiplied by a

proper Air/Fuel ratio in the FFY-535 block. Air/Fuel ratio is assigned by amanual setting station HIC-504. The manipulated variable represents theair quantity needed in order to burn with a predetermined excess air the fuelgas.

CNU Off Gas flowrate is measured by FI-538 and the value is multiplied bya proper Air/CNU Off Gas ratio in the FFY-538 block. Air/CNU Off Gas ratiois assigned by a manual setting station HIC-506. The manipulated variablerepresents the air quantity needed in order to burn with a predeterminedexcess air the CNU Off Gas.

NH3 Rich SWS Off Gas flowrate is measured by FI-518 and the value ismultiplied by a proper Air/ NH3 Rich SWS Off Gas ratio in the FFY-518block. Air/ NH3 Rich SWS Off Gas ratio is assigned by a manual settingstation HIC-505. The manipulated variable represents the air quantityneeded in order to burn with a predetermined excess air the NH3 RichSWS Off Gas.

The 3 contributions calculated above are summed up in the FFY-539Bblock and the resulting manipulated variable represents the total air quantityneeded to burn the combustible gases in order to result the desired degreeof oxygen excess in the tail gas.

The output from FFY-539B block is then compare to the thermal reactortemperature (with the output from TY-560B) in the high signal selector FFY-539A,which selects the greatest signal to reset the setpoint of FIC-539. FIC-539 controlsthe air flowrate from the combustion air preheater to the thermal reactor with FV-539.

FIC-539 is reverse acting: The valve FV-539 opening will be decreased when theprocess variable of FIC-539 increases.


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Figure10:ControlofCom

bustionAirFlowratetoIncinerator


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3.1.7.1. Incinerator Residence Zone Temperature Control (A-2201-H-01)

The control system is deigned to maintain stable and adequatetemperature conditions within the incinerator.

Incinerator residence zone temperature is controlled by TIC-560 acting in

split range control on 2 control valves:

TV-560 controlling the fuel gas flow to the incinerator (In the lowrange (0-50%) signal output from TIC-560)

FV-539 controlling the air flow to the incinerator (In the high range(50-110%) signal output from TIC-560). In this case, TIC-560 is incascade with FIC-539.

When the temperature increases, the controller output first closes TV-560by means of TY-560A while TY-560B output remains zero. In thiscondition the controller action is ignored on FIC-539 set point and FV-539valve remains in its position determined only by the setpoint based on

combustible gases air requirement, as described previously.If the temperature rise continues until TV-560 is fully closed, then TY-560B output is increased and the controller action enters the FFY-539A,thus contributing to the setpoint of FIC-539.

The following DCS printout shows the incinerator section:


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3.1.8. Inter-Unit Controls & Interfaces

There are no inter-unit controls in the SRU.

3.1.9. Operating Parameters

For operating conditions of the SRU refer to the following Process Flow Diagrams:

8474L-022-A0102-4110-300-001 Claus Section Max Distillate

8474L-022-A0102-4110-300-002 Incineration Section Max Distillate

8474L-022-A0102-4110-300-003 Claus Section Max Gasoline

8474L-022-A0102-4110-300-004 Incineration Section Max Gasoline

8474L-022-A0102-4110-300-005 Heat & Material Balance Max Distillate

8474L-022-A0102-4110-300-006 Heat & Material Balance Max Distillate

8474L-022-A0102-4110-300-007 Heat & Material Balance Max Gasoline

8474L-022-A0102-4110-300-008 Heat & Material Balance Max Gasoline

3.2. Instrument List

Refer to attached extracted instrument list: Unit 022 extracted instrument list.xls


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3.3. Main Equipment

3.3.1. Thermal Reactor

The purpose of the thermal reactor is to accomplish the complete oxidation ofhydrocarbons and all the impurities (such as HCN) present in the total feed gasesand to burn approximately one-third of the total H2S to SO2.

The Thermal Reactor (A-2201-R-01) is a 2 zones reaction furnace, each zoneoperating at different temperature:

In the 1st zone all combustion air, all H2S Rich Off gas and a fraction ofARU Off Gas are burnt.

In the 2ndzone the hot flue gas from the first zone and the remaining ARUOff Gas (about 50% of the total ARU off gas) are mixed.

The temperature inside the first zone is approx. 1240C and the temperature offlue gas leaving the reactor is approx. 900C.

The Thermal Reactor Burner is combined burner type with two lances, one forFuel Gas combustion during plant heating up, turndown case, or during refractorydry-out and the other one for acid gas combustion during normal operation.

The Reactor Burner has a lot of ancillaries to assure smooth and safe operation,such as 2 flame scanners, ignitor, etc. A permanent low pressure steam line(Quench) has been foreseen to moderate the flame temperature in the fuel gasrun. The steam requirement shall be approximately 6 kg/kg of fuel gas. Thequench steam flowrate shall be set by the operator to limit the adiabatic flametemperature to 1400C max.

Reaction chamber is internally refractory lined to prote